In a gas turbine installed in a cold area, after air taken from atmosphere is heated, it is taken by the gas turbine.
The reason why intake air is heated in this manner is because, when dense external air (air) falling within an extremely lower temperature range (for example, −20° C. to −30° C.) is taken by a gas turbine as it is, stable combustion of the gas turbine cannot be assured due to lowering of ignition performance or occurrence of combustion vibrations. When air with such an extremely low temperature is taken by the gas turbine, there is such a possibility that moisture in the air is frozen at an inlet of the gas turbine, and frozen ice enters the gas turbine to damage a turbine vane or the like.
In a gas turbine installed in a cold area, therefore, after air is heated by a heating apparatus such as a heat exchanger, it is taken by the gas turbine. In this case, an air temperature is heated up to a temperature (for example, a temperature of about +5° C.) at which the gas turbine can perform stable combustion.
FIG. 5 shows a conventional example of a gas turbine plant installed in a cold area. As shown in FIG. 5, a gas turbine 10 includes a compressor 11, a combustor 12, and a turbine 13 as main members. Air (atmosphere) “A” taken from the outside is taken by the compressor 11 of the gas turbine 10 via an intake air duct 15.
An inlet guide vane (IGV) 11a is provided at an inlet port of the compressor 11, and an air amount taken by the compressor is controlled according to an opening of the IGV 11a. Incidentally, the opening of the IGV 11a is controlled in response to a load state, an operating state, or the like.
A generator 20 is coupled to the gas turbine 10 and it is rotationally driven by the gas turbine 10 to generate electric power.
A heat exchanger 30 for heating intake air is arranged in the intake air duct 15. Steam S with a high temperature (for example, 300° C.) is supplied to the heat exchanger 30 through a steam pipe 31. The heat exchanger 30 heats (performs heat exchange of) air “A” to be taken by the gas turbine 10 utilizing heat of the supplied steam S.
A control valve 32 for controlling an amount of steam caused to flow in the steam pipe 31, namely, an amount of steam supplied to the heat exchanger 30 is arranged in the steam pipe 31.
Incidentally, as steam supplied to the heat exchanger 30, steam generated from an auxiliary steam boiler (not shown), steam generated from an exhaust heat recovery boiler (not shown) which utilizes heat of exhaust gas exhausted from the turbine 13 to generate steam, or the like is used.
Incidentally, the steam generated from the auxiliary boiler is hereinafter called “auxiliary steam”, and the steam generated from the exhaust heat recovery boiler is hereinafter called “self-generated steam”.
A thermometer 40 is attached to a portion of the intake air duct 15 positioned between the heat exchanger 30 and an inlet stage of the compressor 11. The thermometer 40 measures a temperature of air A′ which is heated in the heat exchanger 30 to be taken by the compressor 11 of the gas turbine 10. A measurement temperature t1 of the intake air A′ measured in this manner is transmitted to a control apparatus 50.
The control apparatus 50 includes a deviation calculating unit 50a and a proportional-integral calculating unit (a PI calculating unit) 50b. A target temperature TO (for example, +5° C.) is preliminarily set in the control apparatus 50. The target temperature TO is a temperature preliminarily set in response to characteristic of each gas turbine 10 as intake air temperature which can combust (operate) the gas turbine 10 stably.
The deviation calculating unit 50a of the control apparatus 50 performs deviation calculation between the measurement temperature t1 and the target temperature TO to obtain a deviation temperature Δt (=TO−t1). The proportional-integral calculating unit 50b performs PI calculation to the deviation temperature Δt to output a valve opening instruction P. A valve opening of the control valve 32 is adjusted in response to the valve opening instruction P.
Accordingly, when the measurement temperature t1 is low, the valve opening instruction P takes a large value to increase the valve opening of the control valve 32 so that a steam amount supplied to the heat exchanger 30 is increased. On the other hand, when the measurement temperature t1 becomes high, the valve opening instruction P takes a small value to decrease the valve opening of the control valve 32 so that a steam amount supplied to the heat exchanger 30 is decreased. As a result, feedback control is performed to a steam amount supplied to the heat exchanger 30 such that the temperature of air A′ heated by the heat exchanger 30 to be taken by the compressor 11 reaches the target temperature TO. Thereby, the temperature of the intake air A′ is maintained at a stably combustible temperature.
Incidentally, the present inventor(s), has (have) developed a technique where, when an intake air amount taken by the gas turbine 10 increases/decreases due to opening change of the IGV 11a or the like, the increase/decrease of the intake air amount is detected, a valve opening preceding instruction corresponding to the increase/decrease of the intake air amount is obtained, and a valve opening of the control valve 32 is controlled by an instruction obtained by adding the value opening preceding instruction to a valve opening instruction P and has already filed a patent application about the technique (Japanese Patent Application NO. 2006-313758).
That is, a patent application about an invention of a control apparatus which performs control so as to maintain a temperature of intake air in the target temperature TO by performing preceding (feedforward) control based upon the valve opening preceding instruction in response to increase/decrease of an intake air amount in addition to feedback control based upon the valve opening instruction P, even if the intake air amount increases/decreases rapidly has been filed by the inventor(s).
Patent Literature 1: JPB-4-48921
Patent Literature 2: JPA-2003-161164